1. Field of the Invention
The present invention relates to a data save apparatus for a battery-powered data processing unit, such as a notebook personal computer, a word processor or a hand-held terminal.
Due to the remarkable development of such electronic devices as large-scale integrated circuits (LSIs) which have a high density of electronic parts and are low in power consumption, data processing units are becoming more and more light-weight and small-sized. Also, to make them portable, a battery is used for supplying power to such data processing units. However, if the battery is accidentally removed, data stored in volatile storage may be destroyed or lost when removal of the battery occurs during data processing. Then, the processing must be resumed from the very beginning after the battery is restored or replaced with a new one.
Accordingly, some effective and economical means to overcome such inconvenience is in great demand for a battery-powered data processing unit.
2. Description of the Related Art
FIGS. 1(a) and 1(b) show a battery-powered data processing unit (hereinafter simply called a data processing unit or a unit), an example of which is a hand held terminal (HHT) for a terminal input apparatus as disclosed in U.S. Pat. No. 4,773,032.
In a data processing unit, the following methods are used conventionally to avoid the above-mentioned inconvenience. The first method is to stipulate in a manual to take out the battery only after operating a power-off switch, which causes a data save operation to be performed and, after that, the power to be turned off. The data save operation is performed such that data stored in volatile storage is saved in a non-volatile storage or a magnetic disk, etc. The second method is explained with reference to FIGS. 2 and 3.
FIG. 2 is a perspective view of a housing for batteries and a cover of a data processing unit of the related art. FIG. 3 is a sectional view of the battery housing and the cover shown in FIG. 2.
A battery 2a is a "battery pack" with plural batteries wrapped in laminated vinyl chloride, for example.
A unit 1a is provided with a switch 5a. A cover 3a, which covers the battery pack 2a housed in the unit 1a, is provided with a projection 4a at an end. When the cover 3a is put in position, the switch 5a is pressed by the projection 4a and turns on, i.e., closes. Thus, the switch 5a detects the presence of the cover 3a and that the battery 2a is present and mounted in the unit 1a. A switching transition of the switch 5a from on to off causes a security operation to be performed to save the current status, including register contents and program status, into non-volatile storage, for example, so that the processing which will be suspended by the removal of the battery 2a from the unit 1a, can be resumed later.
When the battery 2a needs to be replaced for a so-constructed unit 1a, e.g., for periodic maintenance or when a power supply voltage drop is detected, data stored in volatile storage can be saved in the non-volatile storage during the period from the time the cover 3a is removed until the battery 2a is taken out, so that the processing, which is thereby suspended, can be resumed later by restoring the data saved.
However, when the unit 1a is dropped accidentally and the cover 3a comes off suddenly by the shock, for example, the power supply is cut off almost at the same time as the absence of the cover 3a is detected by the switch 5a.
Therefore, a problem occurs in that, in such cases, the unit 1a does not have enough time to perform the data save operation, thereby destroying or losing data in the process.